Safety device for low pressure vessels



D s 1942. w, w. MAsoN 2,304,417

SAFETY DEVICE FOR LOW PRESSURE VESSELS FiledJlarch 6. 1940 3 Sheets-Sheet l INVENTOR- f Mo/abrz W Mason.

ATTORNEY 8, 1942. w. w. MASON 2,304,417

SAFETY DEVICE FOR LOW PRESSURE VESSELS s Sheets-Sheet 3 Filed March 6,1940 m R 0% an m ./,.R EW 6 m L In. M H a M 7 m! w 6 M TH m w PatentedDec. 8, 1942 UNITED STATES PATENT, OFFICIE.

SAFETY DEVICE FOR LOW PRESSURE VESSELS Walden W. Mason, Kansas City, Mo.

Application March 6, 1940, Serial No. 322,476

15 Claims.

This invention relates to safety devices for protecting vessels or otherequipment containing fluids under normally slight pressures, for examplestorage tanks for containing volatile hydrocarbon fluids. Tanks of thischaracter are usually constructed for containing only slight pressuresand are structurally incapable of withstanding pressures much above orbelow the normal working pressures, consequently such tanks are equippedwith some form of pressure and vacuum relief valves in order to preventinjury of the tank by excess pressures and to avoid collapse thereofwhen the tanks are emptying. However, most of these valves areinadequate to give proper relief under extreme conditions for the reasonthat they do not hold the required pressure, or they will not operate torelieve pressure at the low pressure desired.

It is, therefore, the principal object of the present invention toprovide a safety mechanism that affords adequate relief of closepressure differentials, usually a few ounces.

Other objects of the invention are to provide a safety device with arelatively large relief opening normally closed by a diaphragm which isreadily disrupted responsive to low pressures; to provide formultiplication of the actuating pressure thereby increasing reliabilityof the device under low working pressures; to provide a diaphragmshearing head normally supported in operative position relative to thediaphragm by a simple and reliable trigger mechanism, readily releasableresponsive to low pressures; and to provide a trip mechanism responsiveto low pressures acting from within or without the vessel.

In accomplishing these and other objects of the invention, ashereinafter pointed out, I have provided improved details of structure,the preferred forms of which are illustrated in the accompanyingdrawings, wherein:

Fig. 1 is a vertical section through a safety de vice constructed inaccordance with the present invention and showing the shear head inlatched position.

Fig. 2 is a detail perspective View of the shear head showing one of thelatch engaging ears detached and in spaced relation.

Fig. 3 is a horizontal section on the line 33 of Fig. 1.

Fig. 4 is a vertical section similar to Fig. 1 but showing the diaphragmshearing head in tripped position.

Fig. 5 is a vertical section through a portion of the device taken atright angles to the section shown in Fig. 1.

Fig. 6 is a detail perspective view of one of the trip levers and itsresilient supports.

Fig. '7 is a vertical section through a modified form of the inventionshowing the shear head in latched position in full lines and in' trippedposition in dotted lines.

Fig. 8 is a horizontal section on the line 8-8 of Fig. 7.

Fig. 9 is a similar horizontal section on the line 99 of Fig. "7.

Referring more in detail to the drawings, and first to the form of theinvention shown in Figs. 1 to 6 inclusive: 7

I designates a safety device which is adapted for connection with avessel or the like contain ing fluidunder slight pressure and foreffecting release of a predetermined high pressure within the tank orapredetermined negative pressure, the device I being connected with thetank by a nipple 2 having suflicient capacity to give the desired reliefwhen dangerous pressures are reached Within the vessel so. as to avoiddisruption thereof.

The device I preferably includes a collar 3 secured to the nipple 2 andhaving a lateral flange 4 and provided with an inclined annular grippingface 5 encircling an opening 6 in the collar which communicatesthroughthe nipple 2 with the in-. terior of the tank. Seated on the face5 is the peripheral marginal edge I of a diaphragm 8 arranged tonormally close flow from the nipple through the opening 6. The marginaledge I of the diaphragm 8 is retained in grippinig engagement with theface 5 by an annular rib 9 having a gripping face Ill engaging theopposite face of the diaphragm margin 1, the rib 9 being formed as apart of an annular flange II corresponding tothe flange 4.

The flanges II and 4 are secured together to effect gripping contactwith the diaphragm by suitable fastening devices, such as bolts I2, ex-

tending through registering openings I3 and I 4 in the respectiveflanges as clearly shown in Fig. 1. The inner diameter of the flange II.corresponds to the diameter of the opening 6 and connected therewith isa housing I5, having an enlarged upper portion I6 for normallycontaining a shear head I I, later described, and which cooperates withthe lower portion of the sleeve to form a ledge H3. The enlarged upperportion IE or the sleeve terminates in a lateral flange I9 for seatingthe collar 20 of a weather-cap 2|. The collar 20 conforms to the innerdiameter of the upper portion of the housing and has a flange 22 securedto the flange I9 by fastening devices such as bolts 23.

The cap 2I includes a substantially conicalshaped cover 24 that issupported above the open end of the collar 23 by brackets 25 to form anoutlet 26 therebetween which is protected by a depending eave 2! of thecap as clearly shown in Fig. 1. Formed in the enlarged portion of thehousing I is an annular offset 23 terminating in one side of the housingin an opening 29. Secured over the opening is an actuator diaphragmhousing 39 including a section 3| having a diaphragm seat 32 forsupporting the marginal edge of a relatively large flexible diaphragm33. The diaphragm 33 is clamped to its seat by means of an annularflange 34 on a complementary housing section 35. The sections 39 and 35of the diaphragm housing are shaped to provide pressure chambers 36 and31 on the respective sides of the flexible diaphragm 33, and one of thechambers, for example 36, is connected with atmosphere preferablythrough the housing I5 by means of a lateral duct 38 registering withthe opening 29, while the other chamber is provided with an opening 39having connection with an opening .40 in the'collar 3 by means of a pipe4I so that the pressure acting on the lower side of the safety diaphragmis admitted to the relatively large diaphragm 33 to cooperate with theatmospheric pressure in the chamber 36 in flexing the diaphragm 33 whenexcess pressure differentials occur in the respective chambers as set bydiaphragm loading springs 42, 43 and 44. The spring 44 is seated on aplate 45 engaging the top of the actuating diaphragm and its oppositeend engages a disk 46 carried on the reduced end 41 of an adjustingscrew 48, the screw 48 being threaded in an opening 49 in a dome-likeextension 59 of the upper diaphragm housing section.

Connected with the plate 45 and bearing against the lower side of theactuator diaphragm 33 is a plate 5| having a boss 52 carrying adepending stem 53 terminating in a coned end 54 which seats in a recess55 of a disk 56 seating the upper ends of the sleeved springs 42 and 43.The lower ends of the springs are carried by a similar disk 51 supportedon the reduced end 58 of-an-adjusting screw 59. The adjusting screw 59is threaded into an opening 60 formed in a plate 6| which closes theopen end of a cylinderlike extension 62 on the lower housing section andwhichprovides an enclosure for the springs 42 and 43.

The spring seating disk 56 preferably carries a buffer washer 63 havingan opening 64 therein to pass the stem 53.. By adjusting the springson-the respective sides of the diaphragm through manipulation of theadjusting screws, the diaphragm may be normally balanced between thedifferential pressures in the respective chambers 36 and 31. Thediaphragm sections are retained in clamping contact with the diaphragmby fastening devices such as screws 35 extending through the flangesthereof and the lower diaphragm section is secured to the housing I5 byfastening devices 66.

In order to prevent unauthorized tampering with the adjusting screws,the heads 61 thereof may be apertured to pass the strand I58 of a seal69,.the strand also passing through lugs I9 as shown in Fig. 1.

Slidable in the upper, enlarged portion of the housing above the ledgeI8 is the shear head I! which includes a ring-like body or weight II of,suitable vouter. diameter .to slide within the.

lower portion I5 of the housing, and which has a peripheral flange I2 atits upper end to engage the ledge I8 and support the shear head when theshear head has been dropped upon the diaphragm 8. The shear headincludes radially arranged blades I3 fixed within slots I4 formed in thelower portion of the ring II. The blades have knife edges I5 whichpreferably diverge outwardly and downwardly to form points It at theouter ends thereof to piercingly engage the diaphragm near its points ofsupport, and to begin shearing cuts across the diaphragm.

Fixed at opposite diametrical sides on the upper end of the ring II areears TI and I8 having flange portions I9 projecting outwardly in spacedrelation with the annular flange F2 for the engagement by latch plates89 therebetween. The ears just described are secured in position byfastening devices such as screws al. The latch plates are carried on theends of supporting bars 82 and 83. The bar 82 includes a bar-like armlocated in the duct 38 and which has springattaching brackets 84 and 85on the respective ends thereof to attach fiat springs 85 and 81. Thespring 8'1 projects downwardly within the spring housing 62 and connectswith an inwardly extending boss 89 by fastening devices 89. The otherspring 89 extends upwardly within the upper portion of the housing I5and is secured to inwardly extending lugs 99 on the side wall thereof asshown in Fig. 4. are normally tensioned so that the lever arm is shiftedtoward the right to retain a contact plate M on the bar 82 normally incontact with a disk-like collar 92 on the stem 53, previously described,and retain the latch plate 89 at the opposite end of the lever armengaged under the ear I8.

The other bar 83 includes a portion 93 extending alongside the bar 82and terminates in a lateral arm 94 carrying a contact plate 95 similarto the contact plate 9| and which engages the opposite diametrical sideof the collar 92. The bar at the opposite end of the shank includes anarcuate portion 95 freely supported in the annular offset 23 of thehousing I5 and which has its free end 91 carrying a latch plate 98engageable under the other ear Tl. The bar 83 is suspended from lugs 99and I99 by flat springs IBI and I92, the spring I02 being attached to alug I03 on the arcuate portion of the arm and the spring)! beingattached to the bracket carry,- ing the latch plate 98. The lateral arm94 which carries the contact plate 95 also has a bracket carrying a flatspring I94 which has its opposite end secured to a lug I95 projectinginwardly of the spring housing similarly to the attachment of the spring81 previously described. The springs IIJI, I92 and I94 are so tensionedthat they shift,

the bar 83 to the left and retain the contact plate 95 in engagementwith the collar 92when the latch plate 98 is engaging under the ear TIto suspendingly support the shear head above the diaphragm.

With the safety diaphragm in position and the actuator diaphragmadjusted so that the collar 92 is retained in engagement with the edgesof the contact plates, at predetermined differential pressure on therespective sides of the actuator diaphragm 33, the shear head isretained in sus pension over the safety diaphragm 8. However, should apressure occur in the vessel below the predetermined minimum, thepressure on the atmospheric side of the actuating diaphragmpreponderates with the result that the springs are thrown out of balanceand the collar 92 is shifted The springs so that the contact plates passthereunder and engage the shank 63 responsive, to action of the leafsprings, consequently the latch plates are spread apart and release theshearhead. The shear head then drops into shearing contact with thediaphragm 8 so that atmospheric pressure may rush into the tank andprevent collapse of the tank. Reversely, should excess pressures ocourin the tank, the diaphragm is moved in the opposite direction so. thatthe contact plates move off of the top edge of the collar 92 tosimilarly release the shear head and effect shear of the diaphragm sothat the excessive pressures are released from the vessel.

When the shear head is actuated to etfectrelease of vacuum in the tank,downward movement of the shear head is stopped by the flange I2 thereofengaging the ledge I8. When excessive. pressure is released there may bea tendency for the shear head to blow outwardly, and to limit themovement thereof the ofiset portion of the housing is provided withclips .I I and I01 having arm portions I08 extending over the upper edgeof the shear head ring as shown in Fig. 5.

After the safety diaphragm has been disrupted, it is necessary toreplace it with a new safety diaphragm and to relatch the shear head sothat the ears thereon engage the latch plates of the spring supportedbars. When normal pressures occur within the vessel as set by thesprings on the respective sides of the diaphragm, the collar 92 is inposition to retain the lever arms with the latch plates in engagementwith the under sides of the ears. Shifting of the bars loads thesupporting springs thereof so that they are effective in shifting thebars in the opposite direction whenever the collar 92 has moved out ofregistry with the contact plates.

In the form of the invention shown in Figs. 7 to 9 inclusive, thehousing I09 for the shear head III] has allateral extension III on theactuating diaphragm side thereof and the diaphragm housing I I2 issecured thereto as shown in Fig. '7. The lower section II3 of thediaphragm housing has 2. depending spring housing II I carrying a guideII5 for the diaphragm stem I II. In this form of the invention, thelower ends of the springs H8 and H9 are carried in a cup-like plug Iadjustably carried by the spring housing to vary compression of thesprings. The opposite end of the springs seats against a washer I2Ibearing against the partition I22 of the spring housing, the partitionhaving an opening I23 to pass a collar I24 on the diaphragm stem III sothat the collar seats against the spring seating washer. Fixed on thediaphragm stem. above the collar I2I is an arm I25 extending throughregistering slots I 26 and I21 in the spring housing and lateralextension III respectively to terminate in a hook I28 adapted to engagea similar hook I29 carried by a ring-like weight I30 which carries theshear blades I3I. The weight I30 is pivotally carried by an arm I32 on ashaft I33 having its end journalled within'bearings I34 and I35 in thesides of the housing extension as shown in Fig. 8. The weight isprovided with a recess I36 on the side thereof opposite the knives tocontain a coil spring I31 having a projecting end I38 engaging againstthe wall of the lateral extension III when the hooks are interengaged asshown in Fig. 9. When the diaphragm is actuated to efl'ect movement ofthe hook I28 relative to the hook I29, the hook I29 is released and thespring acts to throw the shear head IIO into shearin contact with thesafety diaphragm I39. This spring also, serves. as a shock absorber whenexcessive pressures blow the shear head backwardly into the lateralextension. of the housing after the diaphragm has been disrupted.

From the foregoing it is obvious that I have provided a safety devicewhich is well adapted for operation at. relativelylow pressures. It isalso obvious that the shear head of the diaphragm is retained by areliable trip mechanism which is readily released by low pressure due tothe large size of the actuator diaphragm.

What I claim and desire to secure by Letters Patent is: i

1. A safety device, of the character described including a rupturablediaphragm for retaining a pressure medium, means supporting thediaphragm, diaphragm shearing means having cutting edges extendingsubstantially radially with respect to the diaphragm, latch mechanismcarried by the supporting means for suspending the shearing means overthe diaphragm, a trip actuae tor, means for conducting the pressuremedium to the trip actuator, and trip means connected with the tripactuator and the latch mechanism for effecting release of the shearingmeans to effect cuts through the diaphragm by said cutting edges.

2. A safety device of the character described including a diaphragm,supporting means for the diaphragm, a housing carried by the supportingmeans, a shear head in the housing and adapted to move into shearingcontact with the diaphragm, said head having blades arrangedsubstantially radially with respect to the diaphragm, and means in thehousing and subject to differential pressures acting on the diaphragmfor effecting movement of the shear head to bring said blades intoshearing contact with the diaphragm.

3. A safety-device of the character described including a diaphragmsubject to a pressure medium, supporting means for the diaphragm, ahousing carried by the supporting means, a sh ar head in the housing andadapted to move in shearin contact with the diaphragm, latch means inthe housing for supporting the shear head in spaced relation with thediaphragm, pressure actuated means, trip means connecting the pressureactuated means with said latch means, and means for admitting saidpressure medium to said pressure actuated means for effecting actuationof the trip means to release the latch means.

4. A safety device of the character described including a safety head,supporting means for the safety head, a housing carried by thesupporting means, a shear head in the housing and adapted to move inshearing contact with the safety head, latch means in the housing havinlatch engagement with the shear head for supporting the shear headinspaced relation with the safety head, pressure actuated means supportedby the housing, trip means connecting the pressure actuated means withsaid latch means, and means for admitting a pressure medium acting uponthe safety head to said pressure actuated means for effecting actuationof the trip means and release of the latch means.

5. An apparatus of the character described including a housing, adiaphragm in the housing, a shear head, means releasably sup-porting theshear head over the diaphragm, trip means connected'with the shear headsupporting means for releasing the shear head, and trip release meansconnected with said trip means, including a pressure actuated diaphragmhaving opposite sides subject to pressures corresponding with pressuresacting upon the first named diaphragm.

6. An apparatus of the character described including a housing, adiaphragm in the housing subject to a pressure medium, a shear head,shear head supporting means having releasable connection with the shearhead, trip means having movable support in the housing and arranged toshift the shear head supporting means for releasing said connection, apressure actuated diaphragm connected with the trip means, and means foradmitting said pressure medium to act on the pressure actuated diaphragmfor effecting actuation of the trip means to release the shear head.

'7. A device of the character described including a housing, a diaphragmsupported in the housing, a shear head in the housing, a pair of barssupported in the housing and having latch members suspendinglysupporting the shear head over the diaphragm, the supporting means forthe bars tending to urge the latch members into unlatched position,contact members carried by the respective bars, means spacing thecontact members and retaining the latch members in engagement with theshear head, and an actuator connected with the spacing means to shiftsaid spacing means from between said contact members to efiect shift ofthe bars and effect release of the latch members from the shear head.

8. In combination with a vessel for containing liquids under slightpressure including a safety device havin a flow passage connected withthe tank, a diaphragm normally closing the flow passage, a shear head,latch means spacingly supporting the shear head over the diaphragm,pressure actuated means, trip means connecting the pressure actuatedmeans with said latch means, and means for admitting pressure in saidtank to the pressure actuated means whereby the pressure actuated meansis operated to effect actuation of the trip means and release of theshear head and effect disruption of the diaphragm.

9. A device of the character described including a housing, a diaphragmsupported in the housing, a shear head in the housing, a pair of barssupported transversely of the housing and having latch memberssuspendingly supporting the shear head over the diaphragm, thesupporting means for the bars tending to urge the latch members intounlatched position, contact members carried by the respective bars,means spacing the contact members and retaining the latch members inengagement with the shear head, a flexible diaphragm, a housingenclosing said flexible diaphragm and forming chambers on the respectivesides thereof, a stem connecting the flexible diaphragm with saidspacing means, means for admitting atmospheric pressure to one of thechambers, means for admitting a pressure medium to the other of saidchambers, and means for balancing the flexible diaphragm against saidpressures to normally retain the spacing means in engagement with thecontact members and to allow movement of the flexible diaphragm uponchange of pressure in one of said chambers to effect movement of thesupporting bars for release of the shear head.

10. In combination with a vessel for containing liquids under slightpressure including a safety device having a flow passage connected withthe vessel, a diaphragm normally closing the flow passage, shear means,means supporting the shear means over the diaphragm, pressure actuatedmeans, means connected with the pressure actuated means to maintain saidconnection with said supporting means in one position of the pressureactuated means, and duct means connecting the pressure actuated meanswith the vessel for admitting pressure from said vessel to the pressureactuated means whereby the pressure actuated means is operated to effectrelease of the shear means.

11. In combination with a vessel for containing liquids under slightpressure, a safety device includin a housing having a flow passageconnected with the vessel, a diaphragm normally closing the flowpassage, a weighted shear head supported over the diaphragm saidsupporting means having releasable engagement with the shear head, andmeans responsive to pressure in said vessel for releasing shear headfrom the supporting means.

12. In combination with a vessel for containing liquids under slightpressure, a safety device including a housing having a flow opening, adiaphragm normally closing said opening, means for effecting shear ofthe diaphragm, means supporting the shear means in position for theshear means to drop into shearing contact With the diaphragm, and meansfor releasing the shear means from said supported position, said meansbeing responsive to differential pressure between the interior andexterior pressures acting on the vessel for effecting actuation of theshear means upon a predetermined change in said differential pressure,said means including means independent of said pressure differential forefiecting positive action of said shear means.

13. A safety device of the character described including, a housinghaving an inlet for a pressure medium, a rupturable diaphragm supportedin the housing to close said inlet for normally retaining the pressuremedium, diaphragm shearing means, latch mechanism carried in the housingand having releasable connection with the diaphragm shearing means toreleasably' support the shearing means relative to the diaphragm, tripmeans connected with the latch mechanism for effecting release of theshearing means to disrupt the diaphragm, a pressure responsive actuatorhaving operating connection with the trip means, a duct connecting saidinlet with'the pressure responsive actuator through which pressuremedium is conducted to act upon the pressure responsive actuator, andbalancing means acting upon the pressure responsive actuator inopposition to said pressure medium, said balancing means being arrangedto oppose said pressure medium at a predetermined pressure and beingexpandable when the pressure drops below said minimum to effect releaseof said shearing means.

14. A safety device of the character described including, a housinghaving an inlet for a pressure medium, a rupturable diaphragm supportedin the housing to close said inlet for normally retaining the pressuremedium, diaphragm shearing means, latch mechanism carried in the housingand having releasable connection with the diaphragm shearing means toreleasably support the shearing means relative to the diaphragm, tripmeans connected with the latch mechanism for effecting release of theshearing means to dis rupt the diaphragm, a pressure responsive actuatorhaving operating connection with the trip means, a duct connecting saidinlet with the pressure responsive actuator through which pressuremedium is conducted to act upon the pressure responsive actuator, andbalancing means acting upon the pressure responsive actuator inopposition to said pressure medium, said balancing means being arrangedto oppose said pressure medium at a predetermined pressure and beingyieldable when the pressure increases above said predetermined pressureto effect release of said shearing means.

15. A safety device of the character described including, a housinghaving an inlet for pressure medium, a rupturable diaphragm supported inthe housing to close said inlet for normally retaining pressure medium,a diaphragm shearing head, a pair of shift members, spring meansnormally suspending said members in the housing, latch means carried bysaid members having latch engagement with the shearing head to supportthe shearing head above the rupturable diaphragm, a diaphragm housingsupported by the first named housing, a diaphragm in the diaphragmhousing, a trip normally engaged between said shift members to retainlatched engagement of the shearin head, means connecting the trip withthe last named diaphragm to move the trip in one direction, an expansionspring connected with the trip to move the trip I

